The overall goals of the Colorado Learning Disabilities Research Center includes the identification, characterization, and amelioration of learning disabilities. By identification of specific regions of the genome which contribute to phenotypes of learning disabilities, this project interacts directly with the other projects in the Center, most specifically with Projects I, II, and III. Through non-parametric linkage and association analyses, the phenotypes obtained in these projects can be related to DNA markers and then to specific gene mutations. Evaluate of the contributions of each region or gene to a specific phenotype can be done, which can determine if phenotypes are genetically distinct. This work has already shown that there is a gene located on 6p21.3 which affects both phonological and orthographic abilities. In the next years, we will expand this work to allow comparisons of the contributions of additional loci influencing reading disability to the contributions of candidate genes that have been identified as contributing to ADHD. This will be particularly important in determining the genetic basis of co-morbidity for these traits. Identification of the genes influencing reading disability and ADHD will help delineate the basic functions and neurological mechanisms that are crucial for these conditions.